Streams: synchronous xread fixes and improvements.
Streams: synchronous xread fixes and improvements.

antirez/redis,soveran/redis,Sciumo/redis,yossigo/redis,rogerchina/redis,ofirluzon/redis,spinlock/redis,soveran/redis,oranagra/redis,charsyam/redis,Sciumo/redis,Sciumo/redis,rogerchina/redis,antirez/redis,antirez/redis,yossigo/redis,nnog/redis,spinlock/redis,soloestoy/redis,ctripcorp/redis,soveran/redis,pmem/redis,charsyam/redis,ctripcorp/redis,soloestoy/redis,pmem/redis,nnog/redis,pmem/redis,GitHubMota/redis,PKRoma/redis,PKRoma/redis,neomantra/redis,nnog/redis,rogerchina/redis,neomantra/redis,PKRoma/redis,spinlock/redis,pmem/redis,PKRoma/redis,ofirluzon/redis,antirez/redis,yossigo/redis,charsyam/redis,yossigo/redis,yossigo/redis,charsyam/redis,Sciumo/redis,oranagra/redis,spinlock/redis,neomantra/redis,oranagra/redis,ofirluzon/redis,soloestoy/redis,soloestoy/redis,soveran/redis,neomantra/redis,nnog/redis,neomantra/redis,ctripcorp/redis,ofirluzon/redis,rogerchina/redis,GitHubMota/redis,charsyam/redis,soloestoy/redis,PKRoma/redis,GitHubMota/redis,oranagra/redis,ctripcorp/redis,ofirluzon/redis,oranagra/redis,GitHubMota/redis